From U.S. Pat. No. 5,047,391, it is known to produce moldings of high-temperature superconducting material by producing a homogeneous melt from the oxides of bismuth, strontium, calcium and copper in a molar ratio of the metals of 2:2:1:2 in the temperature range from 870.degree. to 1100.degree. C., casting it in molds and then allowing it to solidify. The castings removed from the molds are first heat-treated at temperatures from 780.degree. to 850.degree. C. and finally they are treated in an oxygen atmosphere at temperatures from 600.degree. to 830.degree. C.
In the process for making contact to high-temperature superconductors based on yttrium, bismuth and thallium according to U.S. Pat. No. 4,963,523, the surface of the high-temperature superconducting material is thoroughly cleaned, in a first step, by etching with air excluded and a metallic contact made of noble metals or their alloys is applied directly, in a second step, to the high-temperature superconducting material.
It is also common to apply suspensions of noble metals in the form of a lacquer or paste to high-temperature superconducting material, in which case a fine metal film, to which solder contacts can be applied, remains behind on the surface of the high-temperature superconducting material after the solvent has evaporated.
A disadvantage of the contacts obtained by the known processes is their low mechanical ruggedness. In addition, a heat treatment is usually necessary after applying the noble metal to obtain a good electrical contact, as a result of which the superconducting properties of the material may be adversely affected.